Introduction

Many people in the world are food insecure and are expected to remain so for some time to come (Rosegrant et al., 2001; Food and Agriculture Organization [FAO], 2003c; Shapouri and Rosen, 2003). Food insecurity is associated with low levels of agricultural productivity and/or inadequate purchasing power. Low levels of agricultural productivity may also result in inadequate purchasing power in regions in which sales of agricultural commodities are a major source of income. Emissions of greenhouse gases are expected to affect food security because of their potential impacts, both positive and negative, on agricultural productivity. Of particular concern, however, are the potentially damaging effects of rising temperatures associated with global climate change. Tropical and subtropical nations, which already experience temperatures that are higher than optimal for crop production, are especially vulnerable (Reilly et al. 1996; Gitay et al., 2001). Many of these nations are already food insecure as well.

Explicit estimates of the impacts of climate change on food security, such as the number of people at risk of hunger, are rare (Rosenzweig and Parry, 1994; Parry et al., 1999; Fischer et al., 2002). They are also limited for a variety of reasons. First, estimated impacts are based on changes in climate that are projected to occur in the relatively distant future, 2020 or later. Near-term estimates are not available. Second, the climate projections used in this research are derived from runs of general circulation models (GCMs). GCMs simulate the causal linkages between changing concentrations of greenhouse gases and changes in temperature, precipitation, and other climatic variables. They also strive to reflect regional and local differences caused by atmospheric circulation patterns and the Earth's topography. Nevertheless, uncertainty about projected changes in regional and local climate by GCMs is still relatively high (National Research Council, 2001).

The primary objective of this paper is to evaluate the extent to which global climate change may contribute to food insecurity in the relatively near term, such as 2012. Rather than relying on GCMs, climate change is simulated by extrapolating from long-term changes that occurred during the 20th century. Relying on the past to project the future is still subject to a certain level of uncertainty, but there is likely to be less uncertainty associated with this approach than with projections based on GCMs, especially when using a 10-year timeframe.

In the following, background information is provided on food security and the potential impacts that rising atmospheric concentrations of greenhouse gases might have on it. This includes some current estimates and short-term projections of food security. Next, impacts of climate change on growing-season length are estimated. They were an important determinant of agricultural productivity in some low-income countries during the 20th century. Potential implications of climate-induced changes on agricultural productivity and on food security in the short term are then explored. Finally, implications for management, policy, and research and development options for carbon sequestration in developing countries are discussed.